Huawei SUN2000 Inverter: Smart Dongle Setup and KNX Modbus TCP Integration
Huawei SUN2000 string inverters are among the most widely installed residential and commercial solar inverters in Germany, the Netherlands, and Benelux. Connecting them to KNX requires specific knowledge of the Smart Dongle SDongleA-05, the non-standard Modbus TCP port 6607, and the correct register addresses for power, battery, and grid data — all of which differ from the SunSpec standard.
SUN2000 hardware overview and Smart Dongle requirement
The Huawei SUN2000 range covers single-phase (3-6 kW) and three-phase (5-40 kW) string inverters. The SUN2000-5/6/8/10KTL-M1 and M2 are the most common residential variants in Europe. For KNX Modbus TCP integration, the Smart Dongle SDongleA-05 is required — without it, only RS485 Modbus RTU is available on the inverter COM port, which requires a separate RS485-to-Ethernet converter.
The SDongleA-05 plugs into the USB-A socket on the right side panel of the SUN2000 inverter. It acts as a WiFi or Ethernet bridge and also exposes Modbus TCP on the local network. The Smart Dongle is sold separately and must be ordered from the installer's Huawei distributor — verify compatibility with the specific SUN2000 firmware version before ordering.
Smart Dongle setup — FusionSolar app steps
Prerequisites: - SDongleA-05 inserted in SUN2000 USB-A socket - FusionSolar app installed (installer account required) - Installer account: register at solar.huawei.com/installer Step 1: connect FusionSolar app to Smart Dongle FusionSolar → Device → Add Device → Scan QR code (on Dongle) Or: connect phone WiFi to Dongle AP (SSID: Dongle_xxxxx) Enter Dongle web UI: 192.168.8.1 — set up WiFi or Ethernet Step 2: configure inverter network FusionSolar → Device → SUN2000 settings → Communication Set IP (DHCP or static), subnet, gateway Verify ping to inverter IP from KNX gateway network Step 3: enable Modbus TCP FusionSolar → Device → SUN2000 → Settings → Communication Scroll to Modbus TCP: toggle ON Port: 6607 (fixed, cannot be changed) Access level: installer (required to enable Modbus TCP) Step 4: verify Open Modbus Poll: IP = Smart Dongle IP, Port = 6607, Unit ID = 0 Read registers 32000-32070: manufacturer string in 32000-32014
SUN2000 Modbus register map
Huawei uses a proprietary Modbus register map that differs from the SunSpec standard. All registers are holding registers (function code 3), big-endian byte order. Register addresses are 1-based in Huawei documentation — subtract 1 for 0-based Modbus Poll or gateway configuration that uses 0-based addressing.
SUN2000 holding register map (FC3, 1-based, big-endian)
Power and production:
32064-32065: Active Power (int32, 1W resolution)
Positive = generating, 0 during night
32078-32079: Daily Energy Yield (uint32, 0.01 kWh)
Reset at midnight
32091: PV1 Input Voltage (uint16, 0.1V)
32092: PV1 Input Current (uint16, 0.01A)
32093: PV2 Input Voltage (uint16, 0.1V)
32094: PV2 Input Current (uint16, 0.01A)
Battery (LUNA2000 connected):
32087: Battery SOC (uint16, 0.1%) — multiply by 0.1 for %
32114-32115: Battery Charge/Discharge Power (int32, 1W)
Positive = charging, Negative = discharging
32103: Battery Voltage (uint16, 0.1V)
32105: Battery Current (int16, 0.1A)
Grid:
32261: Grid Power (int32, 1W)
Positive = exporting, Negative = importing| Register | Parameter | KNX DPT | Conversion |
|---|---|---|---|
| 32064-32065 | Active Power (W) | DPT 9.001 (kW) | Divide by 1000 |
| 32087 | Battery SOC (%) | DPT 5.001 (%) | Divide by 10 |
| 32114-32115 | Battery Power (W) | DPT 9.001 signed | Divide by 1000, signed |
| 32261 | Grid Power (W) | DPT 9.001 signed | Divide by 1000, signed |
| 32078-32079 | Daily Yield (kWh) | DPT 13.013 (Wh) | Multiply by 10 (0.01kWh to Wh) |
KNX Modbus gateway configuration for SUN2000
LOYTEC LROC-100 and Weinzierl 5010 are both suitable for Huawei SUN2000 integration. The LOYTEC LROC-100 is preferred for multi-protocol installations where BACnet or M-Bus devices are also present. The Weinzierl 5010 is simpler and widely used in residential KNX projects.
Weinzierl 5010 configuration for Huawei SUN2000
Device settings in ETS plug-in: IP address: <Smart Dongle IP> Port: 6607 (CRITICAL — not 502) Unit ID: 0 (CRITICAL — not 1) Protocol: Modbus TCP Poll task 1 — Active Power: Start register: 32063 (0-based = 32064 - 1) Count: 2 (32-bit int32) Data type: 32-bit signed integer, big-endian Value transform: divide by 1000 (W to kW) KNX GA: 6/0/1, DPT 9.001 (kW) Poll interval: 10 seconds Poll task 2 — Battery SOC: Start register: 32086 (0-based) Count: 1 (uint16) Data type: 16-bit unsigned integer Value transform: divide by 10 (0.1% to %) KNX GA: 6/0/3, DPT 5.001 (0-100%) Poll interval: 60 seconds Poll task 3 — Grid Power: Start register: 32260 (0-based) Count: 2 (int32) Data type: 32-bit signed integer, big-endian Value transform: divide by 1000 (W to kW) KNX GA: 6/0/5, DPT 9.001 signed Poll interval: 10 seconds
SG Ready and forced charge via Modbus write
The SUN2000 LUNA2000 battery system supports work mode control via Modbus write, equivalent to SG Ready input on heat pumps. Writing register 47500 forces the battery into specific operating modes. Combined with KNX logic reading a dynamic electricity tariff signal (Tibber API via Node-RED, or ENTSO-E spot price via Home Assistant), the battery can automatically charge during cheap overnight tariff periods.
SUN2000 battery work mode register — Modbus write
Register 47500: Storage Control Mode (holding, FC6 write)
Write 0: self-use mode (default — prioritise self-consumption)
Write 5: forced charge mode (charge at max rate)
Write 6: forced discharge mode (discharge to grid/loads)
Write 2: time-of-use mode (uses TOU schedule)
Register 47075: Forced Charge/Discharge Power (uint16, W)
Write desired charge power in watts
Example: write 3000 = charge at 3 kW
KNX to Modbus write via Weinzierl 5010:
KNX GA '6/1/0' DPT 1.001 = 1 (cheap tariff signal)
→ Weinzierl 5010 write command: reg 47500 = 5 (forced charge)
→ Weinzierl 5010 write command: reg 47075 = 3000 (3 kW)
KNX GA '6/1/0' = 0 (normal tariff):
→ Write reg 47500 = 0 (return to self-use mode)
Tibber integration:
Home Assistant Tibber integration → cheap_tariff entity
HA automation: when cheap_tariff = true
→ write 1 to KNX GA '6/1/0' via HA KNX integration
→ Weinzierl 5010 triggers Modbus write to SUN2000Troubleshooting port 6607 connection issues
Port 6607 connection failures are the most common SUN2000 KNX integration issue. The failure modes differ from standard Modbus TCP errors because the non-standard port is often blocked or the Modbus TCP feature is not enabled in the FusionSolar app.
Troubleshooting checklist — port 6607 refused or timeout
Symptom: Modbus Poll → Connection refused on port 6607 Check 1 — Smart Dongle IP reachability: ping <Smart Dongle IP> from laptop on same network If ping fails: check DHCP lease or set static IP in FusionSolar Check 2 — Modbus TCP enabled in FusionSolar: FusionSolar app → Device → SUN2000 → Settings → Communication Confirm Modbus TCP toggle shows ON This is the most common root cause — Modbus TCP is OFF by default Check 3 — Port 6607 not blocked by router: Test from laptop: nc -zv <dongle IP> 6607 If blocked: add port forwarding rule in router for port 6607 (only needed if KNX gateway is on different network segment) Check 4 — Unit ID must be 0: Symptom: connection succeeds, all registers return 0x80 exception Root cause: unit ID set to 1 instead of 0 Fix: change unit ID to 0 in Modbus Poll and gateway config Check 5 — Wrong IP (WiFi vs Ethernet): Smart Dongle has two IP addresses if both WiFi and Ethernet active Use the IP on the same network as the KNX Modbus gateway
Huawei SmartLogger 3000 for commercial sites: for commercial installations with multiple SUN2000 inverters, the SmartLogger 3000 aggregates all inverter data and exposes Modbus TCP on the standard port 502 with inverter register offsets. This simplifies KNX gateway configuration significantly for multi-inverter systems — a single gateway device entry handles all inverters via the SmartLogger.
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